What is Depth of Field?
Depth of field is one of the most misunderstood and mislabeled things in web video and photography. Most people think depth of field means images with soft fuzzy backgrounds with blobs of coloured light. But that’s not true. That’s called bokeh. You can watch my video about bokeh here.
Depth of Field simply means: Depth of Focus
- If your scene is like that one described above, it has shallow depth of field.
- If everything from front to back is in focus, it has deep depth of field.
How to control depth of field
Most people think f-stop is the only thing that controls depth of field.
But depth of field is actually controlled by a combination of these three things:
- f-stop (also called aperture or lens opening)
- proximity to your subject
- focal length
How f-stop affects depth of field
Most entry level cameras come with a zoom lens that has a maximum f-stop range of f 3.5 to f 5.6. To see the f-stop of your lens, just take a look at the front of the lens or the lens barrel. See the photo below. That number is the biggest f-stop your camera can be set to. And the smallest f-stop is usually f 22 or thereabouts.
- A lens set with a large f-stop will usually give you shallow depth of field.
- And a lens set with a small f-stop will give you deep depth of field.
- But you need to keep the other things like proximity and focal length in mind as well, because they also control depth of field. More about those next.
How proximity affects depth of field
Proximity to your subject is the next factor that affects depth of field. The closer you are to your subject, the less depth of field you will have. You can see that demonstrated in the photos at the top of this post. I’m really close to the mushrooms so there is only a slice of the photo that is in focus.
How focal length affects depth of field
A short focal length lens has a wider angle of view. This would be the type of lens you might use for a landscape scene or when shooting video in a small office space. A short focal length (wide angle) lens will give you deep depth of field.
A long focal length lens has a narrower angle of view, and you can see things further away. This is also called a telephoto lens. You would use this kind of lens for a portrait or in a scene where you’re trying to bring something close, like wildlife. A telephoto lens gives you shallower depth of field than a wide angle lens.
Many cameras come with zoom lenses that have a range of focal lengths. Entry level cameras usually come with lenses that go from wide angle to medium telephoto. So they are a good all-around lens. Keep in mind that you also get optical differences when using a wide angle or telephoto lens.
Here’s a focal length quick tip: Don’t shoot a portrait of someone you love using a wide angle lens. You will distort their face and make them look wider. No one wants that, unless you’re going for comic effect.
Before you run out and buy a lens that opens up to f 1.8, trying creating shallow or deep depth of field using a combination of two out of three of the methods above to get your desired result.
- For shallow depth of field try: large f-stop + long focal lens
- For shallow use a largish f-stop and get close to your subject, but don’t use a wide angle lens
- For deep depth of field, use a wide angle lens. A wide angle lens usually has deep depth of field no matter what f-stop you use
For general web video settings:
- For deep depth of field use a normal lens (not too wide, not too tele) and a small f-stop – This is perfect for video if you’re shooting outdoors and want to show some landscape in focus behind you
- For shallow depth of field use a normal lens (not too wide, not too tele) and a large f-stop – This is also perfect for video if you’re shooting indoors in front of some distracting backgrounds in your room. I use this setup at about f 5.6 and I’m happy with the result. If there is still too much in focus, set your camera on f 4.0.